Black and white photos do so well at capturing emotion, and I've always loved the way some photographic methods can make the darkness and light in them so much more sharp.
There's so much to be said for the world of color and the way to capture that on film, but when you're looking at the world in black and white I think you're forced to see it more realistically. There isn't anything else to distract you.
I just sort of went off there, sorry. These are just my views on it of course! We've been studying black and white portraiture in my classes this semester.